ASTM E975-22

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E975 − 22
Standard Test Method for
X-Ray Determination of Retained Austenite in Steel with
1
Near Random Crystallographic Orientation
This standard is issued under the fixed designation E975; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The volume percent of retained austenite (face-centered cubic phase) in steel is determined by
comparing the integrated chromium or molybdenum X-ray diffraction intensity of ferrite (body-
centered cubic phase) and austenite phases with theoretical intensities. This method should be applied
to steels with near random crystallographic orientations of ferrite and austenite phases because
preferred crystallographic orientations can drastically change these measured intensities from
theoretical values. Chromium radiation was chosen to obtain the best resolution of X-ray diffraction
peaks for other crystalline phases in steel such as carbides. No distinction has been made between
ferrite and martensite phases because the theoretical X-ray diffraction intensities are nearly the same.
Hereafter, the term ferrite can also apply to martensite. This test method has been designed for
unmodified commercial X-ray diffractometers or diffraction lines on film read with a densitometer.
Other types of X-radiations such as cobalt or copper can be used, but most laboratories examining
ferrous materials use chromium radiation for improved X-ray diffraction peak resolution or
molybdenum radiation to produce numerous X-ray diffraction peaks. Because of special problems
associated with the use of cobalt or copper radiation, these radiations are not considered in this test
method.
1. Scope necessary, the users can calculate the theoretical correction
factors to account for changes in volume of the unit cells for
1.1 This test method covers the determination of retained
austenite and ferrite resulting from variations in chemical
austenite phase in steel using integrated intensities (area under
composition.
peak above background) of X-ray diffraction peaks using
chromium K or molybdenum K X-radiation. 1.6 Units—The values stated in inch-pound units are to be
α α
regarded as standard. The values given in parentheses are
1.2 The method applies to carbon and alloy steels with near
mathematical conversions to SI units that are provided for
random crystallographic orientations of both ferrite and aus-
information only and are not considered standard.
tenite phases.
1.7 This standard does not purport to address all of the
1.3 This test method is valid for retained austenite contents
safety concerns, if any, associated with its use. It is the
from 1 % by volume and above.
responsibility of the user of this standard to establish appro-
1.4 If possible, X-ray diffraction peak interference from
priate safety, health, and environmental practices and deter-
other crystalline phases such as carbides should be eliminated
mine the applicability of regulatory limitations prior to use.
from the ferrite and austenite peak intensities.
1.8 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.5 Substantial alloy contents in steel cause some change in
ization established in the Decision on Principles for the
peak intensities which have not been considered in this
Development of International Standards, Guides and Recom-
method. Application of this method to steels with total alloy
mendations issued by the World Trade Organization Technical
contents exceeding 15 weight % should be done with care. If
Barriers to Trade (TBT) Committee.
1
This test method is under the jurisdiction of ASTM Committee E04 on
2. Significance and Use
Metallography and is the direct responsibility of Subcommittee E04.11 on X-Ray
and Electron Metallography.
2.1 Significance—Retained austenite with a near random
Current edition approved Nov. 1, 2022. Published February 2023. Originally
crystallographic orientation is found in the microstructure of
approved in 1984. Last previous edition approved in 2013 as E975 –13, which was
withdrawn in July 2022 and reinstated in November 2022. DOI: 10.1520/E0975-22. heat-treated low-alloy, high-strength steels that have medium
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E975 − 22
(0.40 weight %) or higher carbon contents. Although th
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